Fishing tool



RECORDING AMMETER RECORDING AMMETER May 2 1944- T. c. WHERRY 2,347,759

FISHING TooL Filed March 29, 1941 CURRENT SOURCE THOMAS C. WHERRY BY l v' Patented May 2, 1944 FISHING Toor.

Thomas C. Wherry, Bartlesville, Okla., assgnor to Phillips Petroleum Company, a corporation of Delaware Application March 29, 1941, Serial No. 385,927

5 Claims.

This invention relates to apparatus for locating and recovering objects in well bores.

During the processes of drilling and producing wells, it is sometimes necessary to recover from the well bore, tools or other objects which have become disconnected from the surf ace equipment.

Ordinarily it is diflicult for the operator at the surface of the earth to determine when the lost require several days before the lost equipment is successfully recovered from the well bore. An advantage which this invention offers to the practice of fishing is that it enables the operator t determine when the tool is near the object to be recovered, whether the object has been picked up, and at any point on the way out, whether it is still attached.

An object of this invention is to provide improved apparatus for locating and recovering objects in well bores.

Another object of this inventionis to provide apparatus for determining at any time during a fishing operation whether an object is attached to the fishing tool.-

Figure 1 is a vertical cross section through a well bore illustrating diagrammatically a preferred embodiment of the present invention.

Figure 2 is a vertical cross section through a well bore illustrating diagrammatically a modification ofthe present invention.

Figure 3 is a verticalgcross section through a Well bore illustrating diagrammatically another modication of the present invention.

With reference to the drawing, the numeral I designates a well bore in which an overshot fishing tool 5 is suspendedin the well bore by an extensible and retractable electrical conductor 6, which is insulated from the fluid in the well and provides for lowering and raising the fishing tool in the well bore. The insulated conductor 6 maybe separate from the tool suspension means if desired. The fishing tool 5 is provided with slips 'I whiclrg'age the equip-V4 terial, preferably metal, and contains equipment for detecting the proximity of radioactive substances, an arrangement of the well-known Geiger-Muller counter II being shown. A potential is applied across the Geiger-Muller counter II by the batteries I2 and the high impedance Geiger-Muller counter matched to conductor E by the transformer I3. When the counter is excited by gamma rays emanating from capsule 9, short pulses ofv current are produced in the counter circuit and these pulses are transmitted through conductor 6 to the amplifier I4 at the surface of the earth. After amplification the pulses of current pass to the recording frequency meter I5`which makes a record of the radioactive emanations picked up by the Geiger-Muller counter. The electrical circuit including `the recorder is completed through the earth to which the amplifier is connected. v

The operation of the apparatus shown in Figure 1 is as follows: Objects which are likely to be lost during drilling operations, for example, drilling tools and service instruments, are pre-V pared prior to their introduction into the well bore by bolting, Welding or otherwise attaching to the object the capsule containing radioactive material. In the event that the object is lost in the well bore, a suitable fishing tool, equipped 1 as shown in Figure 1, is lowered into the well, and its approach t0 the lost object is indicated by the instruments at the top of the well. This is due to an increase in the intensity of radioactive emanations picked up by the Geiger- Muller counter from the previously placed source of radioactive emanations. When no further increase in radioactivity is indicated the tool is in close proximity to the object. After the customary movements of the fishing tool are carried out in an attempt to pick up the sh, the tool is raised in the well bore. If the concentration of radioactivity decreases, the iish is not attached to the tool and the operator is able to return the tool to the proper location by a motion of only a few feet. After each attempt to pick up the fish the tool is raised in the well bore. If the radioactivity does not decrease, the object is attached to the tool, and may be withdrawn-from the well bore. Furthermore, at all times during the trip out, the attachment of the object to the tool is indicated by the instruments at the surface.

In Figure 2, the body of tool 5 is made up of two portions, one portion I1 being made of metal and the other portion I8'being made of material of relatively low magnetic permeability, Bakelite being an example of such material. Portion I8 of the body is equipped with a ycoil of wire I9, having one end grounded to part I1 of the body by any suitable electrical connection 20, and the other end connected to conduclobject enters the magnetic eld set up by Ithe 22 through current indicator or recorder 23 across conductor 6 and the ground.

The operatiori of the apparatus shown in Figure 2 is as follows: This system may be used to iish for any object which is made of a material of relatively high magnetic permeability. The tool is lowered into the well bore, and as .the

l coil I9 of the detector, the reluctance of the 1magnetic circuit decreases and the inductance increases. causes a decrease in the current inthe circuit, which varies with the position of the object in the electromagnetic field, and the operator .is thus informed of the relative po'sitions of the object' and tool by the action of the current indicator at the surface of the earth. As described with reference to Figure 1, the. `attachment of the fish to the toolmay be ascertained at any time. l

InFi'gure, the body of tool 5 is made up of two portions, one portion 2l being made of metal and the other portion 25 being made of la non`-` conductor, such as Bakelite. This nonconduct- '2 ing portion of the body is equipped with two contact springs 26 and 21. The contact 26 is grounded to part 24 of the body -by any suitable electrical connection 28,V and the contact 21 is connected to conductor E by insulated conductor 3 29. Only a small area is exposed to the fluid in the well by contact 21. The body 24, 25 of the tool may be made entirely of one/material, such as metal, and spring contact 21 insulated from the body. Contact 26 may be omitted if desired, the engagement of the iish with contact 21 being sufiicientto change the effective area exposed to the fluid in the well. -.A' constant voltage is applied by current source 30 between the cond uctor 6 and the ground. The ammeterA 3|, in- 4 -terpsed between the source of current 30 and the conductor indicates the amount of current flow-v ing in the electrical circuit.

The operation of the uapparatus shown in liigy ure 3 is as follows: This'system may be used to shfor any' object made of an electrical con- However, unlike the systems ducting material. described above, it. is not responsive to the proximity of an object `and the tool, -but only to contact of an object with the tool. The two contact springs are so spaced' as to en'- able the object to make electrical contact between them. The area of the contact surface 21 is preferably small so that only a small surface is i exposed to the iluid of the well` bore. A small current may flow through the electrical circuit due to the .conductivity of the wall fluid. An increase in. the area `thus exposed to the fiu.ii\`

allows an increased-current to iiow. 'I'his oc-l curs whenupon lowering the fishing tool into e the well bore, the iish makes electrical connection .between the contacts or with contact 21 only. In this way, the operator is informed of the en -A gagement of tool and sh.- By observation of the ammeter 3l the operator may readily determine when the iishing tool is 'correctly positioned rela- A tive tothe nsn and whether or not'the hshis attached on. the up trip of the fishing tool.

In the drawing and the foregoing .detailed description of this invention, the fishing tool shown and described is of .the ytype known in the in' dustry as an overshot. fishing tool. It is to be' understood -that thepresent invention'is not to be confined to use with this type tool. The aplplication of this invention to other types of fishing tools will be apparent to those skilled in the art. .Various changes may be made in the size,

shape and relative position of the parts withoutdeparting from the spirit ofv the invention. Il claim: j

1. In apparatus for locating and recovering an .object in a well bore, thecombination comprising a housing that is open at its lower end and that is adapted to be moved throughthe well bore and -to receive at least a portin\\\of the object through said open lower end, means. within the housing. for engaging the object whenla predetermined `portion thereof has been received in the housing, an electric circuit including'means within the housing and responsive electrically to variations 1n the distance between-the housing. i

and the object, a source of electric current, and

an indicator responsive toelectrical variations` inthe circuit.

2.The combination in accordance with the preceding claim wherein the dirst mentioned means isadapted to releesably grip 'the object when a predetermined portion thereof has been received in the housing.

3. In apparatus for locating and recovering a magnetic object in a well bore, the combination comprising a housing that open at its lower end and that is adapted to be moved through the well bore and to receiveat least a portion of the object through said open lower end, means within the housing for 'engaging the object when a predetermined portion thereof has been received in the housing, an electric circuit including a detector contained in the housing and re-. Asponsive to the magnetic permeability of the object, and an indicator exterior the well bore in electrical communication with the detector.

4. In apparatus for locating and recovering a magnetic object in a well bore, the combination comprising a. housing thatis open at its lower end and that is adapted to be moved through' the well bore and to receive at least a portion of theobject through said open lower en d, means within the housing for engaging the object when a predetermined portion thereof has been received `in the housing, an electric circuit including coiled detector means carried by the housing andiorming a passage into which at least a portion of the object -is adapted to be disposed, and an indicator exterior the well bore in electrical communication with the detector means.

5. In `apparatus for locating and recovering a magnetic object in a well bore, the combination comprising a housing that is open at its lower end and that is adapted to be moved through the well bore and to receive at least a portion of the object through said open lower end, means within the housing for engaging the object when a predetermined portion thereof has -been received in the housing, an electric circuit including coiled detector means in the housing intermediate the above mentioned means and the open end of the housing andforming a passage into .which at least a portion of the object is adapted to tbe disposed, said detectormeans being responsive to the magnetic permeability of the object, and an indicator exterior the well bore communicationw-ithsthe detector means.

. l i THOMAS'C. .WHERRY.

in electrical 

